A geochemical investigation of pressure solution and the formation of veins in a deformed greywacke |
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| Authors: | Alastair Beach |
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| Institution: | 1. Department of Geology, Liverpool University, Great Britain
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| Abstract: | Pressure solution and vein formation often occur simultaneously in shear zones during the deformation of sedimentary rocks. The mineralogical and chemical variations around a typical example of an en echelon zone of quartz veins from north Cornwall are discussed in detail. Solution of quartz is confined to the shear zone and occurs along discrete surfaces. Accumulation of insoluble minerals along these surfaces gives rise to spaced pressure solution cleavage. Petrographic data show that during pressure solution the breakdown of felspar and epidote results in the crystallisation of clay mineral, quartz and siderite. Redistribution of silica within the shear zone by pressure solution does not account for all the quartz in the veins, or for the observed increased concentration of iron and calcium. It is concluded that material was introduced from an external source into the shear zone. |
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